This invention relates to thin layer chromatography plates. More specifically, this invention relates to thin layer chromatography plates capable of performing two dimensional thin layer chromatography.
A number of thin layer chromatography plates which include more than a single layer on their surface are known. For example, U.S. Pat. No. 3,623,841 discloses a two layer plate for thin layer chromatography consisting of a first layer covering a minor portion of the plate which is of a composition suitable for separating amino acids from accompanying interfering substances (e.g., a strongly basic or strongly acidic polystyrene-based ion exchanger), and a second layer covering the remainder of the plate which is of a composition suitable to perform adsorptive thin layer chromatography of amino acids. The first layer of this patented plate does not perform any development of the amino acids along a first direction. Rather, this layer merely performs a washing operation to separate the amino acids from contaminants. The only development of the amino acids occurs in the second dimension, i.e., on the adsorptive layer.
U.S. Pat. No. 3,623,841 also mentions in its background section a prior thin layer chromatography plate suitable for two dimensional chromatography of fats and fatty acids. The plate is said to have a strip which is impregnated with silver nitrate. In the first dimension, the mixture is separated on the impregnated strip in accordance with the number and position of its double bonds. In the second dimension, a transition occurs from the impregnated strip to the non-impregnated layer where further separation of the mixture of substances is effected. The separation in the first dimension along the silver nitrate impregnated strip takes place by argentation thin layer chromatography.
The above prior art techniques have limited utility. For example, they do not provide for separation and determination of certain important materials, such as the separation of sulfonamides, separation of bile acids, and separation of pesticides and pharmaceuticals and their metabolites. A thin layer chromatography plate and method which could accomplish separation of such materials quickly, easily and accurately is accordingly very desirable.